Igneous Petrology Course Lecturer: Matt Genge, Meteorite Researcher, Previously worked at The Natural History Museum. Lectures: Part I (4 weeks) Igneous Processes at the Atomic Scale. Part II (4 weeks) Igneous Processes at Large Scales. Practicals: How to recognise and describe igneous rocks in hand specimen and thin section (see list on handout sheet). Coursework (20%): Five coursework pieces focused on each major group of igneous rocks. 1.5 hour Exam (80%): Straight after christmas! Special revision session last practical.

Hot Under the Collar (part I) Melting and the Phases of Matter Pacaya Volcano - Guatemala Igneous Rocks: formed by cooling of a magma.

The Four Phases of Matter Liquid Solid Gas Plasma

Structural Differences Configurational entropy (disorder)

Kinetic Differences Vibrational entropy (disorder)

Entropy The entropy of a mixture is higher than a pure material

Entropy Entropy increases with temperature due to the magnitude of atomic vibrations

Entropy Entropy is “wasted” or unavailable energy

Total Thermodynamic Energy in Matter + Potential Energy Kinetic Energy Total Energy (Enthalphy H) = PE + KE

Gibbs Free Energy G – Gibbs Free Energy (energy available for chemical work) H – Enthalpy (total energy) S – Entropy (energy locked up in disorder – wasted energy) G = H – T.S First Law of Thermodynamics

Extrinsic and Intrinsic Properties Extrinsic properties depend on the mass of the system.

Extrinsic and Intrinsic Properties Intrinsic Taste Colour Specific Gravity Temperature Extrinsic Volume Amount of Alcohol Attractiveness

Extrinsic and Intrinsic Properties Intrinsic Composition Temperature Pressure Extrinsic Volume/mass Enthalpy Entropy Gibbs Free Energy

Temperature Temperature is the effect of the motions of atoms within a material (the vibrations, translations and rotations of molecules). Temperature is proportional to the average kinetic energy of the atoms or molecules within a material.

Pressure Pressure is the force applied by rebounding atoms and is related to the change in momentum.

Transitions between the Phases of Matter

Transitions and Gibbs Free Energy The phase with the lowest Gibbs Free Energy at equilibrium is the stable phase. Two coexisting phases have the same Gibbs Free Energy

Melting Sudden increase in disorder on melting. A discontinuous increase in entropy S.

First & Second Order Phase Transitions G = H – T.S  H is the latent heat of fusion Temperature stays constant until all the material has melted.